The present invention generally relates to motor and pump assemblies and more particularly relates to a motor-and-pump assembly having reduced vibration characteristics.
German published patent application DE 196 32 167 A1 discloses a generic assembly which comprises an electric motor and a piston pump that are appropriate e.g. for use in an ABS (anti-lock system), TCS (traction slip control) or ESP (Electronic Stability Program) system of a controlled vehicle brake, and pistons of the pump are drivable by way of an eccentric. In this publication, a drive shaft of the electric motor and a support axle of the piston pump have a separate design. Further, a three-ring bearing having an eccentric intermediate ring is arranged on the support axle. However, the eccentric intermediate ring has an uneven mass distribution so that an unbalance will occur when an eccentric of this type is used in a motor-and-pump assembly. The unbalance will produce undesirable noises during operation and load the respective bearings and the support axle and the pump housing in which the support axle is arranged to a major degree.
In view of the above, an object of the present invention is to improve upon an assembly of the type referred to hereinabove so that simple provisions permit reducing the unbalance and, thus, achieving an enhanced quietness in operation and reduced load on the bearings or the support axle and the pump housing.
According to the p resent invention, this object is achieved in that in a generic motor-and-pump assembly, at least one counterbalance weight is additionally provided in the proximity of the eccentric.
Preferably, the counterbalance weight is connected directly to the drive shaft or by the intermediary of a sleeve.
Advantageously, the counterbalance weight may be designed integrally with the intermediate ring.
As an alternative, however, the counterbalance weight may also be connected to the intermediate ring by way of the sleeve.
Preferably, the counterbalance weight is sintered and, hence, especially easy and simple to manufacture.